Bags, such as film bags, are utilized extensively in modem society for containing a wide variety of items, such as candies, food items and liquids. A typical film bag is made from a laminate that includes an outer film layer adhesively secured to an inner sealing layer. The outer layer is usually made from a material that facilitates printing. The inner layer is usually made from a material that enables the package to be sealed. Other layers are also sometimes incorporated into the bag. Properties, such as permeability to oxygen and moisture, strength, stiffness and other packaging requirements may dictate material selection in a given bag design. Most film bags, however, are made from outer and inner plastic film layers, such as polyethylene or polypropylene.
In order to entice a customer to purchase a product, manufacturers typically incorporate promotional advertisements into the product's packaging. For film bags, the promotional advertising has generally been limited to printed indicia on the outer layer of the bag, or ancillary labels that are applied on top of the outer layer.
There have also been attempts over the years to incorporate advertising and/or promotional items, such as coupons, stickers and game pieces, into a product's packaging. The incorporation of such promotional items onto packaging is particularly appealing for products directed toward children, such as candy. For game pieces, such as an instant win game piece, it is typically important that the game piece not be visibly discernable from outside the package. The prior attempts at forming a package with promotional indicia that is not viewable from outside the package typically required the indicia to be hidden by one or more of the layers of the package. For example, U.S. Pat. No. 5,127,743 discloses a package with an entrapped game piece. The outer layer of the package obscures the printed piece from being viewed from outside the package.
U.S. Pat. No. 4,846,504 discloses a multi-layer label for a package. The label includes hidden printed indicia formed on the back of the outer layer. A water soluble adhesive holds the outer layer to the inner layer.
U.S. Pat. No. 4,308,679 discloses a laminated package with a peelable outer layer portion made from a pliant material, such as glossy finished paper. The peelable portion has printing formed on its inner surface which is viewable only when the peelable portion is removed from the remainder of the package. A release agent prevents the peelable portion of the outer layer from adhering to the inner layer.
U.S. Pat. No. 5,076,613 discloses a package label laminate which includes hidden indicia which is discernable from the outside of the laminate only when the laminate is folded to overlap two layers of printed markings.
U.S. Pat. No. 4,281,762 discloses a label for applying to a package. The label includes a removable portion with printed indicia on its inner surface that is obscured from view until the removable portion is detached from a base sheet.
U.S. Pat. No. 4,993,753 discloses a hidden message laminate which includes a transparent outer layer and an inner layer with printing formed on the inner layer. An opaque layer of printed ink is formed on the outer surface of the outer layer and is located so as to overlay and obscure the printing on the inner layer. The opaque layer can be removed by rubbing to expose the hidden printing.
U.S. Pat. No. 3,900,219 discloses a document with a concealed marking. The document includes an upper sheet that has removable portions which cover hidden text. An intricate overprint is added to the back surface of the document to prevent viewing the hidden text from the rear sheet.
Many of the prior art packaging arrangements use an opaque layer of metallic ink, e.g., gold ink, which is applied to the outer layer to completely block or obscure the hidden indicia. The printed indicia is then formed on the metallic block. There is, however, a tendency of the metallic ink to bond to the inner layer, thus preventing the outer layer from being easily separated. This occurs because the inside layer of the package is typically corona treated to facilitate laminating. Metallic ink, however, contains stearic acid which, when combined with a treated surface, creates stearates which can adhere to surfaces.
To prevent bonding of the metallic ink to the inner layer, calcium carbonate is sometimes added to the metallic ink to reduce its bonding potential. However, the calcium carbonate also tends to reduce the adhesion of the metallic ink to the outer layer. As a result, the metallic ink sometimes separates from the outer layer, rendering the hidden indicia illegible.
A need, therefore, exists for an improved film bag which includes a hidden indicia on a portion of the outer layer that can be easily viewed by separating the layers of the film bag without damaging the printed indicia.